March Is Trisomy Awareness Month

NICHD Research Advances Understanding of Trisomy Conditions

Boy with Down Syndrome blowing bubbles

Most people have 23 pairs of chromosomes in most or all of their cells for a total of 46 chromosomes in all. These chromosomes include DNA and other material that provide a blueprint for “building” a person.

Some people have trisomy conditions—those related to having an extra chromosome in most or all of their cells, for a total of 47 chromosomes in all.

An extra chromosome can cause a variety of health problems ranging from mild intellectual and developmental disability (IDD), to severe physical problems.  

During Trisomy Awareness Month in March, the NICHD joins other agencies and organizations in raising awareness about trisomy conditions and the challenges they may pose to individuals and families. Research on these conditions—from their origins, to their mechanisms, to their treatments—plays an important role in the lives of these individuals and families. Select a link below to learn more about trisomy conditions and NICHD research.

About Trisomy Conditions
Down Syndrome Consortium
Other NICHD Activities
More Information

About Trisomy Conditions

Trisomy occurs when a person has a full or partial extra chromosome in most or all of his or her cells—47 chromosomes total.

The specific health issues of a trisomy condition and how severe those issues are depend on:

  • Which chromosome: An extra copy of some chromosomes is lethal; for example, an embryo with three copies of chromosome 1 will not develop.
  • Whether there is a partial or complete extra chromosome: If cells include only a partial extra chromosome, symptoms are usually milder than if cells have a complete extra chromosome.
  • How many cells have the extra chromosome or partial chromosome: If the extra chromosome is in only a few cells, the symptoms are usually milder than if the extra chromosome is in all or most of cells.

Health conditions and problems associated with trisomy include physical abnormalities, such as extra fingers or toes; physiological issues, such as irregular heartbeat patterns; and problems related to intellectual and developmental functioning.

Most of the time, trisomy conditions are not passed from one generation to the next, but result from a random error that occurs during cell division very early on in development.

Trisomy can occur with any chromosome, but the most well-known syndromes are:

  • Trisomy 21, more commonly known as Down syndrome, occurs in 1 in 691 live births in the United States each year, according to the Centers for Disease Control and Prevention. People with Down syndrome usually have mild-to-moderate intellectual and developmental disability (IDD), heart abnormalities, and are at risk for hearing and vision loss and a number of other health conditions. Learn more about Down syndrome on the NICHD Down Syndrome: Condition Information webpage.
  • Trisomy 18, also called Edwards syndrome, occurs in about 1 in 5,000 live births each year in the United States. Infants with Trisomy 18 often have severe IDD, as well as serious heart problems and other life-threatening issues that make them less likely to live past their first birthday. Learn more about Trisomy 18 at Genetics Home Reference Trisomy 18 webpage.
  • Trisomy 13, also called Patau syndrome, occurs in about 1 in 10,000 to 16,000 live births each year worldwide. Trisomy 13 is associated with more severe IDD and multiple physical problems, including serious heart problems. Learn more about Trisomy 13 on the Genetic Home Reference Trisomy 13 webpage.


Down Syndrome Activities and Consortium

NICHD efforts related to Down syndrome have been ongoing since the Institute was established in 1962. NICHD research on Down syndrome includes intramural scientists at the NICHD and extramural researchers who study Down syndrome at other institutions and universities with support from the NICHD.

In 2011, the NICHD led members of the NIH Down Syndrome Working Group, other agencies, and national Down syndrome organizations in forming the Down Syndrome Consortium. This Consortium is a public-private collaboration that focuses on implementing the NIH Research Plan on Down Syndrome, a comprehensive blueprint for NIH Down syndrome research efforts that was drafted in 2007.

The Consortium recently launched a website——to provide a central portal for addressing research needs, communicating research findings, and accessing resources related to Down syndrome, including the National Down Syndrome Patient Registry.

Establishment of a National Down Syndrome Patient Registry was a primary recommendation of the 2007 Research Plan. The Registry, which is anticipated to launch in July 2013, will facilitate communication and information sharing among families, patients, researchers, and parent groups. It will also encourage data collection for research biorepositories and will make it easier for patients to take part in clinical studies on Down syndrome. For more information, visit


Other NICHD Activities

The Institute also supports the following projects related to trisomy conditions.

  • The Neonatal Research Network, supported by the NICHD, is studying the health outcomes for infants born with Trisomy 13 and 18.

The Institute remains dedicated to understanding trisomy conditions as a way to help individuals and families live longer, healthier lives.


More Information

For more information about trisomy research, select one of the following links:

Originally Posted: March 15, 2013


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